Perfect aspect doesn't exist without context because the context creates the necessity for it. Present perfect can be used as a single sentence as the context is assumed. "I haven't seen you for ages" when? - up to now, so it requires present perfect by default. In your example "I have got three children" "have got" is simply the synonym of "have", you can assign it under the same rule of present perfect but it's in fact an idiom of a sort. As for past and future perfect, they need more context to be used. ''They had got (or ''gotten'') a special grant from the Institute'' requires previous context which would tell us about some past actions which would justify the use of past perfect. Alone this sentence doesn't make sense. The same would be with future perfect.

Elena's explanation is brief and clear. The best explanation that I've seen in a long time.

Hey Mike, how are you? I hope you are doing just fine! Let's review your sentences, shall we? 1) ''They had got (or ''gotten'') a special grant from the Institute''. = in this case, I must say it is rather ambiguous as it could mean either that they managed to have a special grant from the Institute (Past Perfect Tense) or that they had (in the sense of ''owned'') a special grant from the Institute. 2) ''I have got three children'' = in this case, it simply means that the person has three children. * May I provide you with additional information? ''Have got'' is often used in conversation and in less formal writing with the same meaning as ''have''. E.g.: ''You have got a problem''. E.g.: ''I have got much to do now.'' E.g.: ''She has got a reckless child''. ''Have got'', ''has got'', and ''had got'' are not usually pronounced in full. When you write down what someone says, you usually write 've got, 's got, or 'd got. E.g.: ''I've got her address''. E.g.: ''He's got a beard now''. ''Have got'' is usually used in the present tense. You don't usually use ''have got'' in future or past forms. Instead, you use ''have'', for example: ''Will you have time to eat before you go?'' (not ''Will you have got time...'') ''I had a cold and couldn't decide whether to go to work''. (not ''I had got a cold...'') Hope that helps!!! :) Should you have any further doubts, do not hesitate to contact me. I shall be pleased to help.

Your teacher fooled you -- Past Perfect can be used alone very well.